Summary

The large-scale Atlantic Ocean circulation moves warm, saline near-surface water from the tropics to far northern latitudes, where it cools, sinks, and returns southward at depth. The fundamental role of this Atlantic Meridional Overturning Circulation (AMOC) for the past, present, and future climate is regularly assessed in the Intergovernmental Panel on Climate Change (IPCC) reports, including the most recent special report on global warming of 1.5°C (1). However, observations of the AMOC are sparse, and scientific knowledge is mainly based on model simulations. On page 516 of this issue, Lozier et al. (2) estimate the strength of the AMOC from the subpolar North Atlantic based on 21 months of continuous observations from the OSNAP (Overturning in the Subpolar North Atlantic Program) array (see the photo).